If you left your latest fishing trip empty-handed, it might not be your fault this time. Colorado Parks & Wildlife reported Saturday a “total fish kill” at St. Vrain State Park’s Pelican Pond.
CPW initially noted substantial losses in January when officials collected what was mostly carp. But that was in between two separate freezes. Now, CPW says fish collected was probably all that was left over after foraging by larger fish, carrion, and raptors.
Further sampling didn’t get much better.
Fish biologist-conducted electroshocking yielded zero fish
Large gillnets yielded just 4 carp after 3 days.
For comparison, gillnets on Blue Heron Reservoir typically yield over 1,000 fish after just one day.
How did this happen? CPW says several factors played a large role. These include low water levels, drought, high water temperature and overactive vegetation. Consequences were exacerbated by untimely freezes and the absence of a fall turnover.
Turnover is critical for the health of lakes and ponds. That’s when cool surface temperatures and wind cause warm water on top to mix together with cool water below redistributing oxygen and nutrients. When that doesn’t happen, it’s bad news for fish.
When oxygen levels drop too low, fish kills follow. Lake freezes, too, reduce oxygen availability.
Nutrient cycling feeds the life on which fish feed, from plankton to insects.
Blessing in disguise? CPW plans to fully replace the area’s old aeration system which should help. It’s a long overdue upgrade since initially being damaged more than a decade ago.
It was installed in 2012 but damaged during the famous floods of 2013.
Damaged continued following sedimentation at the diffusers until only one line was functioning.
What about the fish? CPW will restock the water but it won’t have all the comm carp, gizzard shad, and bullhead.